Well here's my two cents...
The Bimmer 8 series is a great car, its timeless. I think you should make an opportunity to drive the Porsche you are considering.
After driving it you may very well decide that its not for you. I personally think you'll never wanna drive anything else after driving the Porsche.
I have owned several different makes of cars. I've owned several Bimmers i.e. 540, M3. I've had Audi S4s the B5 and B6 chassis. I've owned 2 Lotus esprits. the list go's on.
All these were great drivers and beautiful cars. Between owning all these makes and models, i have owned 5 Porsches, 911s and 928s.
I just keep coming back to Porsche, specifically the 911. Its a different kind of driving experience. Its raw, its gritty, its driving not riding. No power steering, no cup holders. You hear the motor working, you feel the road. Some love them others hate them. I believe true drivers love them.
As for owning both... As someone else said here if your money is long then put them both in your stable. If not make a choice cause its not gonna be cheap to maintain both these cars.
My True Driver